WASHINGTON — The cost of rental housing has increased faster than wages, making it increasingly difficult for low-income families to afford even modest apartments, an advocacy group said yesterday.

"The picture is similar to past years, but it's getting worse," said Danilo Pelletiere, research director of the National Low Income Housing Coalition.

Hawai'i has the most expensive rental costs in the country, followed by California, Massachusetts, New Jersey and New York. California also had eight of the 10 most expensive counties for rental housing, led by Marin County, near San Francisco.

West Virginia had the most affordable rents, followed by Arkansas, North Dakota, Alabama and Mississippi.

The coalition, which advocates for more affordable housing, issues a report each year tracking rental costs in every state, county and metropolitan area in the country.

It says families should spend no more than 30 percent of their incomes on housing and utilities, a standard recognized by many housing experts. Under that standard, the coalition said it could not find a single county in the United States where a full-time worker making minimum wage could afford a one-bedroom apartment.

In reality, the report found, many low-income families spend a far larger share of their incomes on housing.

Nationally, families have to make an average of $15.78 an hour to afford a two-bedroom apartment, while spending no more than 30 percent of their earnings on housing costs. That is up from $15.37 a year ago.

The federal minimum wage, at $5.15 an hour, was last increased in 1997.

Fifteen states — including Hawai'i — have minimum wages higher than the federal level. However, Hawai'i's average wages remain below the national average, mostly because much of the state's job growth has been in the low paying service industry.

Sheila Crowley, president of the housing coalition, said rising housing costs have forced many families to "double up," moving multiple families into apartments designed for only one.